SEO - what is seo and how does it work

when you enter a query in a search engine and type 'enter' you get a list of website results that contain that query term. Users normally tend to visit websites that are at the top of this list as they perceive those to be more relevant to the query.  websites rank better than the others then you must know that it is because of a powerful web marketing technique called Search Engine Optimization (SEO).

SEO is a technique which helps search engines find and rank your site higher than the millions of other sites in SEO is all about optimizing a web site for Search Engines. SEO thus helps you get traffic from search engines.

How to Work Search Engine  ?

• Crawling - is the process of fetching all the website pages and linking to all the web site. This task is proceed by a software, called a crawler or a spider (or Google-bot).
• Indexing - is the process of creating index for all the fetched web pages and keep that into a there database from where it can later be retrieved. Essentially, the process of indexing is identifying the  no\umber of words on that best describe the page and assigning the page to particular keywords.
• Processing - When a search request coming to search engine, the search engine processes it . i.e. it compares the search string in the search request with the indexed pages in the database.
• Retrieving Results - The last step in search engines' activities is retrieving the best matched results. Basically, it is nothing more than simply displaying them in the browser.

Search engines such as Google and Yahoo! often update their relevancy algorithm number of times per month and year. When you see changes in your rankings algorithmic something else outside of your control.
Although the basic principle of operation the minor differences between their relevancy algorithm lead to major changes in results relevancy.